1. Field of the Invention
The present invention relates to a control circuit for a vibration type driving device (vibration wave motor).
2. Related Background Art
In a known vibration type driving device (vibration wave motor control circuit), a circuit for changing the width of a pulse to be input to a switching element for applying a driving voltage to a motor is constituted by an analog circuit, as disclosed in Japanese Laid-Open Patent Application No. 64-8873.
In the above-mentioned prior art, the circuit for changing the pulse width suffers from the following drawbacks associated with the use of an analog circuit:
(i) A signal is easily disturbed by noise. PA1 (ii) Since D/A conversion is necessary when the circuit is controlled by a computer, a large number of D/A converters are required, resulting in high cost. PA1 (iii) The control circuit is not suitable for an IC structure; and when a digital arrangement is to be adopted, if the resolution is increased, then the number of logic elements is increased, thus considerably increasing manufacturing costs.